Yamaha tri moto ytm200k blowing head light bulb

[Tanman496]

Hi I am new to the site and am looking for some help. I have a 1983 Yamaha Ytm 200k that keeps blowing the head and tail light, I replaced the lighting coil and it still does it after running a few minutes. As you give it throttle the bulb get brighter till it blows. Thanks in advance for any help.

[350for350]

Sounds like it may be the voltage regulator to me.

[atc007]

Yes, your regulator is bad.

[Tanman496]

The machine has no voltage regulator I thought the same it has a pull start only from the factory. It has a cdi and a magneto and a lighting coil.

[placek59]

Are you using 12v bulbs of the correct wattage?

Your problem sounds exactly like what happens on my old honda bikes when the battery goes bad. Those bikes use the battery as a voltage regulator and if it's bad, the bulbs blow as soon as it gets revved up over, maybe 6k rpm...

Is there an inline fuse somewhere that you can check? A fuse would typically either let something work or not work though. Just a thought

[Jd110]

I'm still learning this but could it be the magneto? You've got red/yellow from magneto to dimmer switch. Can you check voltage there while revving it? Also, I would suspect a floating ground somewhere. I wouldn't think it would be a ignition coil issue. Just my .02 cents. https://uploads.tapatalk-cdn.com/20170923/7b3578a3b9d1b491dbaf090bb7699b92.jpg
http://www.3wheelerworld.com/oldsite/WiringYamaha.shtml

[Tanman496]

There is no battery cause it uses a magneto which produces its own voltage after it starts from the pull cord and there is no inline fuses.

[Tanman496]

Hey jd110 the red/yellow wire comes from the lighting coil which is under the same cover where the magneto is I have that same diagram and I already replaced the lighting coil and it did not solve the problem so I figured before I spent any more money I would look for help here.

I'm still learning this but could it be the magneto? You've got red/yellow from magneto to dimmer switch. Can you check voltage there while revving it? Also, I would suspect a floating ground somewhere. I wouldn't think it would be a ignition coil issue. Just my .02 cents. https://uploads.tapatalk-cdn.com/20170923/7b3578a3b9d1b491dbaf090bb7699b92.jpg
http://www.3wheelerworld.com/oldsite/WiringYamaha.shtml

[Jd110]

Welcome Tanman, I don't see a lighting coil in the drawing. Must be one since you replaced it.
I have no experience with this set-up, just going off drawing and enough electrical knowledge to be dangerous lol. So you've got 12V ac going to the headlight. Is the tail light working? I ask, because if not, your headlight can blow. Also, check all connections, including light sockets.
Again, if your ground connection is loose or corroded, lights will blow. Inspect the wires throughly, as its 34 y/o. A little troubleshooting knowledge helps, so you might have to research a bit. Stick with, you'll figure it out[emoji4]

[Tanman496]

JD yes the tail light works as well but will blow also if I leave the switch to the on position. I cleaned the ground connection to rule that out but it still did it. As far as voltage I believe it's getting more then 12volts act because as you rev the throttle the bulbs get brighter and brighter till it blows out.

[Jd110]

Well, yes it has to be on for the light to blow. Thing is, if I'm not mistaken, both lights need a working bulb to function properly. Otherwise, you'll get too much juice going to one light. I think. Sometimes it takes awhile for others to reply. But, you might get it by then. Electrical problems can be a bear!

[fabiodriven]

Ya he already said the taillight is working JD. I'm very curious about this issue as well. I wish I had more to add.

[atc007]

My apologies. I was sloppy and assumed this was an electric start machine. So,it was blowing both bulbs. You replaced the lighting coil,,,the big brass one,,checked wiring and grounds,and the tail is less likely to blow now? Or the same? Have you measured voltage yet? If you have a good one with probe,you can see what you have out of your stator on R/Y, and see where it leads you. Let us know. I've never seen this one before! There are some older Polaris quads that will not run with a blown neutral/reverse or taillight bulb!

[MonroeMike]

...I don't see a lighting coil in the drawing...

A different page from the manual showing it.

[Jd110]

A different page from the manual showing it.

I realized it was there last night, so hopefully I didn't scare him off.
A multimeter would be helpful. So, he checks the resistance at the lighting coil. Checks each wire and all connections. Make sure headlight AND tail light have continuity. Is there something else?
If you have any more knowledge here, it would be cool to here more from you, if time allows. Thanks

[Tanman496]

Guys thanks so much for trying to help I can build a 1000hp drag race engine but when it comes to working with a/c current I get confused. Like I said before I did replace the lighting coil to rule that out. The magneto looks almost the same as he lighting coil but it has some sort of wrap around the copper winding and I figured it could be bad or maybe the cdi but don't want to guess.

[MonroeMike]

Testing procedure.

[atc007]

Guys thanks so much for trying to help I can build a 1000hp drag race engine but when it comes to working with a/c current I get confused. Like I said before I did replace the lighting coil to rule that out. The magneto looks almost the same as he lighting coil but it has some sort of wrap around the copper winding and I figured it could be bad or maybe the cdi but don't want to guess.

As long as you replaced the bare copper coil,it is the lighting. I was not doubting you ;). The other coil is strictly for spark. Like I said,it is meter time. Without a regulator, the resistance is built into the coil. You could have gotten a bad new one. Not likely. Clean your switches,very simple. Just tear apart and make sure they are shiny clean. Spiders love to build nests in them. Spray them out with ether or electrical cleaner. But your problem is most likely a 34 YO wire. You should be honored to have Monroe Mike post in your thread . He is the king.

[Jd110]

Testing procedure.

That's great! Thank you, Mike.

[Tanman496]

Thanks guys I will have to find a meter that will test a/c current as mine only does d/c . What would you recommend?